The present invention relates to a semiconductor device fabrication method and pattern formation mold.
To achieve the processability and mass-productivity of fine patterns of, e.g., 100 nm or less in the semiconductor device fabrication process, the nanoimprinting lithography technique that transfers a pattern by bringing a patterned mold into contact with a substrate to be processed such as a wafer is attracting attention.
The nanoimprinting method is a technique by which a master on one surface of which a predetermined pattern to be transferred is formed, i.e., a mold is brought into contact with an imprinting material such as a resist layer formed on a substrate by coating, and the pattern is transferred by setting the imprinting material.
Known examples of the nanoimprinting method are thermal imprinting methods mainly using a thermoplastic resin disclosed in patent references 2 and 3 (to be described later), and optical imprinting methods using a photosetting resist disclosed in patent references 4 and 5 (to be described later).
As an example of the nanoimprinting methods, an outline of the sequence of pattern transfer performed by the optical nanoimprinting method will be described below.
The optical imprinting method comprises steps of (1) coating a substrate to be processed with a photosetting resin, (2) aligning the substrate and a mold and bringing them into contact with each other, (3) setting the resin by irradiation with light, (4) releasing the material from the mold, and (5) removing the residual film. In the residual film removing step, anisotropic etching using an oxygen plasma is mainly used.
In semiconductor lithography, the process advances to a step of etching an undercoat after pattern transfer is performed by the nanoimprinting method.
The optical nanoimprinting method SFIL developed by Molecular Imprints Inc., U.S.A. is a method expected to be applied to semiconductor lithography.
In this SFIL, however, a wafer is coated with an imprinting material serving as a resist for each shot, and control is performed such that the imprinting material spreads inside the shot. Therefore, almost no imprinting material exists in a region connecting the shots.
In this region, no element pattern is formed. Generally, this region is a dicing region, and an aligning mark or an underlying pattern such as a monitor pattern of some kind is formed in the region.
In the conventional imprinting method, however, the region connecting shots is not covered with the imprinting material.
Accordingly, a plasma or the like damages the underlying pattern in the etching step after imprinting. This interferes with operations such as alignment after that, and decreases the yield.
References disclosing the conventional nanoimprinting methods are as follows.
Japanese Patent Laid-Open No. 2000-194142
U.S. Pat. No. 5,772,905
Japanese Patent Laid-Open No. 2003-77807
Japanese Patent Laid-Open No. 2001-68411